Preheat the oven to 375F/190C.
Warm the oil in a medium skillet/frying pan. Finely dice the onion and crush or finely dice the garlic. Remove the stems from the chard, trim the ends then finely slice the stems, cutting into smaller pieces if thick.
Add the onion to the pan, cook a minute then add the garlic and chard stalks. Cook for around 3-5 minutes until soft but not brown.
Meanwhile chop the chard leaves fairly finely and slice the anchovy fillets. Drain, rinse and chop the capers. Add the chard leaves to the pan once onions are soft, stir in so they wilt, around a minute or two. Add the anchovies, capers and fennel seeds and mix in well.
Remove the mixture from the heat and add the pine nuts, golden raisins, cheese and breadcrumbs and mix well. Note this filling can be made ahead and refrigerated overnight.
Stuff each of the squid relatively full but take care not to overstuff - leave around ½in/1cm space at the end.
Place the stuffed squid in a baking dish with a little olive oil under them. Arrange the tentacles on either side and cover them with any remaining stuffing over them. Put a little salt and pepper over everything and drizzle lightly with olive oil.
Bake for approx 20 minutes until the squid has firmed up, is no longer translucent and you'll see juice from the squid in the dish. Serve with a little chopped parsley over the top and a squeeze of lemon. Nice served with pasta, bread, salad or on their own.